Method and device of forming piles molded in the ground by filling thin sheathings



July 27, 1954 E. PICKMAN METHOD AND DEVIC E OF FORMING PILES MOLDED IN THE. GROUND BY FILLING THIN SHEATHINGS Filed Feb. 20, 1951 n L M MM mm r r M v I x 1 f UNITED STATES ?ATENT OFFICE METHOD AND DEVICE OF FORMING PILES MOLDED IN THE GROUND BY FILLING THIN SHEATHINGS Edgard Pickman, Brussels, Belgium, assignor to Compagnie Internationale des Pieux Arms Frankignoul, Socit Anonyme, Liege, Belgium Application February 20, 1951, Serial No. 211,909 Claims priority, application France March 3, 1950 3 Claims.

It is known to form piles moulded in the ground by driving into the latter a sheathing from thin sheet metal, by means of a removable mandrel which increases the rigidity thereof during driving, the sheathing, which is left in the ground, being filled with concrete or the like after Withdrawal of the mandrel.

The invention relates to a method of and a device for forming piles of this type, which render such formation particularly simple and judicious.

According to the invention, the sheathing is formed of at least one frusto-conical section,

and driving thereof is effected by means of a hollow mandrel having a corresponding outer taper and extendin up to a certain distance from the lower end of the sheathing, the driving of the whole being effected by applying a driving force, especially the impacts of a rammer upon a tight plug from compressed material, e. g, dry or slightly wet concrete which has not set, which plug extends in the lower end of the hollow mandrel and in the portion of the sheathing projecting below the mandrel.

Further features and advantages of the invention will appear from the disclosure of an example of embodiment, which will be given hereinafter with reference to the accompanying drawings, wherein:

Fig. 1 shows a vertical cross-sectional View of the assembly at the beginning of the driving.

Fig. 2 shows the position of the various members at the end of the driving,

Figs. 3 and 4 show two subsequent stages in the formation of a pile, and

Figs. 5 and 6 show vertical cross-sectional views of the lower end of the alternative constructional forms of a sheathing according to the invention.

In the example illustrated, the sheathing includes two frusto-conical sections from thin sheet metal I, 2, but it will be understood that the number of sections may be varied at will.

The sections of the sheathing are positioned on the desired, site on the ground, being nested in one another, and a mandrel 3 in the form of a tubular body is inserted inside the innermost section. The mandrel has an outer surface made up of steps the dimensions and the taper of which correspond respectively to those of the various sections of the sheathing. The lower end of the mandrel 3 has an outer diameter greater than the inner diameter of the lower end of the sheathing, so that, when the mandrel is engaged in the lower section l of the sheathing, the latter section will project a small distance beyond the mandrel, so as to form a chamber A under the mandrel.

An amount of dry or slightly wet concrete, or any other compressible material which may be used to form the foot of a pile, is then discharged so as to fill the chamber A and a certain height B of the hollow 4 of the mandrel. By striking by means of a rammer 5 upon the concret or the like, a compressed plug 6 is formed, part of which fills up the chamber A, whereas the remaining, for instance somewhat greater, part thereof is located in the lower end of the mandrel. The plug adheres strongly to the inner wall of the mandrel, so that, by proceeding further with striking upon the plug, the mandrel is driven into the ground with the sheathing section I. The plug #5 insures tight sealing of the lower end of the mandrel and of the section I.

When the section I is nearly completely driven into the ground, it engages the section 2, while the corresponding portion of the mandrel comes into contact with the said second section, which takes hence part into the driving. The conical interfitting, in l, of the sections I and 2, provides a perfect seal by mutual jamming'thus making it possible to avoid joining the two sections by welding, which is always expensive and tricky. Driving of further possible sections is accomplished in the same way.

When the required depth has been reached (Fig. 2), the mandrel 3 is hooked to its cables 3 and is raised while the concrete is bein expelled. To facilitate this step, the plug may be softened by addition of water. Thus, the whole of the concrete plug passes into the section I (Fig. 3) and the mandrel is unwedged from the latter section. When the mandrel is being disengaged, there is no chance for the section 1 to be lifted therewith, even if the friction from the ground should be insufiicient to prevent this, since the action of the rammer on the plug presses the latter strongly against the end portion of the said section and retains the latter effectively.

Hence the expanded foot 9 may be formed (Fig. 4) by driving out the plug situated inside the section I and by ramming batches of concrete successively discharged into the said section, so as to force the concrete into the ground. The shaft of the pile may then be concreted in the usual manner in the sheathing, possibly after reinforcement assembly has been placed in position It will be seen that the present invention makes it possible to use a very thin sheathing owing to the large surface of contact between the sheathing and the mandrel which is eifective in driving the sheathing. The lower end of the sec- 3 tion i may be reinforced by an inner (I in Fig 5) or outer ring (H in Fig. 6), though this is not indispensable. The upper outer diameter of the inner ring I0 is substantially equal to or a little smaller than the lower outer diameter of the mandrel.

The inner surface of the mandrel is substantially cylindrical, at least at the lower end, in which the plug is to be formed. This has the special advantage of facilitating the withdrawal of the mandrel 3 when the plug 6 is expelled into the section I after the driving has been completed. In order to reduce the weight of the mandrel, the inner diameter thereof may be increased progressively or gradually.

It is to be understood that the invention is not limited to the example described and illustrated, and that numerous modifications may be made therein without departing from the spirit of the invention. The mandrel illustrated might serve for driving a sheathing made up of three sections, the upper section not being necessarily supported by the mandrel. If desired, the latter may be provided at its upper end with assembling means, e. g. an inner or outer screw thread, which enables to fit an extension member thereto in order to conform the length of the mandrel to a larger number of sheath sections.

What I claim is:

1. In a method of driving into the ground a thin sheathing made up of at least one frustoconical section of downward taper, which method consists in engaging therein a hollow removable mandrel of corresponding outer taper and having its lower end spaced a distance above the lower end of the sheathing so as to leave a part of the latter projectin beyond the mandrel, discharging into the assembly a quantity of compressible unset material, compressing the said material so as to form a sealing plug extending within the lower end of the mandrel and the part of the sheathing projecting below the mandrel, driving the assembly into the ground by applying a driving force on the top of the sealing plug, and

withdrawing the mandrel while simultaneously expelling the material from the mandrel into the sheathing.

2. In a method of forming a pile in the ground, which method consists in placing on the ground a thin sheathing made up of at least one frustoconical section of downward taper, engaging therein a hollow removable rigid mandrel of corresponding outer taper and having its lower end spaced a distance above the lower end of the sheathing so as to leave a part of the latter projecting beyond the mandrel, discharging into the assembly a quantity of compressible unset material, compressing the said material so as to form a sealing plug extending within the lower end of the mandrel and the part of the sheathing projecting below the mandrel, driving the assembly into the ground by applying a driving force on the top of the sealing plug, withdrawing the mandrel while simultaneously expelling the material from the mandrel into the sheathing, and filling the sheathing with pile forming material.

3. A hollow mandrel for driving into the ground a thin sheathing made up of at least one frustoconical section having a downward taper, comprising a tubular body for insertion into the sheathing, said body having an outer taper corresponding to the inner taper of the sheathing, the outer diameter of the lower end of the tubular body being greater than the inner diameter of the lower end of the sheathing, the inner wall at the lower end portion Of said tubular body is substantially cylindrical.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,236,556 Goldsborough Aug. 14, 1917 1,836,140 Upson Dec. 15, 1931 FOREIGN PATENTS Number Country Date 616,470 France 1926 

